Thermal Isomerization Rates of New Azoquinoline-Functionalized Copolymers as a Function of Substitution Patterns

Herein, the impact of chromophore substitution patterns on the optical properties and material motions of newly synthesized side-chain methacrylic copolymers functionalized with azo dyes based on 8-hydroxyquinoline are investigated. The optical properties, specifically absorption spectra, are investigated using spectrometry and quantum-chemical time-dependent density functional theory calculations. Molecular-scale movements are observed by examining the thermal stability of cis isomers of chromophores. These findings reveal that the character of the substituents (electron-donating/withdrawing), as well as the substitution pattern, affects the difference in the excited and ground states dipole moments, the extent of the highest occupied molecular orbital-lowest unoccupied molecular orbital gap, and the parameters describing intramolecular charge transfer upon excitation. These factors contribute to the range of bathochromic shifts in the absorption spectrum. Additionally, the results reveal two species engaged in thermal isomerization, and the bathochromic shift of absorption correlates with their thermal isomerization rates and their contribution to the process. Understanding the dual role of substituents in shaping optical properties and thermal relaxation kinetics is giving perspectives for the design of azo-functionalized polymers with tailored photoresponsive behaviors for advanced applications in optoelectronics.